Variable pulley assembly

ABSTRACT

The disclosure illustrates a variable pulley assembly that may only be adjusted in a nonrotating state. When the pulley assembly is tightened in this state one of the sheaves making up the pulley is displaced away from the other sheave against a spring. The spring returns the displaced sheave to its proper position when the pulley assembly rotates.

United States Patent Wolf et al.

[54] VARIABLE PULLEY ASSEMBLY [72] inventors: David L. Wolf; Robert A.Stelzer, both of Coldwater, Ohio [73] Assignee: Avco Corporation,Coldwater, Ohio [22] Filed: Aug. 3, 1970 211 Appl. No.: 60,521

[52] U.S. Cl ..74/230.l7 [5 l] Int. Cl ..F16h 55/52 [58] Field of Search..74/230.l7 TL, 230. l7 C, 230.17 B

[56] References Cited UNITED STATES PATENTS 2,694,316 ll/l954 Hultin..74/230.l7 TL Feb. 1,1972

Williams ..74/230. 1 7 TL 2,994,228 8/l96l Osborne Primary ExaminerC. J.Husar An0rneyCharles M. Hogan and Gary M. Gron [5 7] ABSTRACT Thedisclosure illustrates a variable pulley assembly that may only beadjusted in a nonrotating state. When the pulley assembly is tightenedin this state one of the sheaves making up the pulley is displaced awayfrom the other sheave against a spring. The spring returns the displacedsheave to its proper position when the pulley assembly rotates.

6 Claims, 2 Drawing Figures PATENTED FEB 1 i972 INVENTORS. DAVID L. WOLFBY ROBERT A STELZER ATTORNEYS.

VARIABLE PULLEY ASSEMBLY The present invention relates to pulleyassemblies and more particularly to variable pulley assemblies.

Variable pulley assemblies have long been used in the farm equipmentindustry. A typical use of this device is in the air blower whichsupplies a fiow of air to separate chaff and other material from shelledcorn. it is frequently necessary to adjust the speed of this blower tovary the separation according to changing field conditions.

These pulley assemblies generally comprises a pair of sheaves axiallydisplaceable toward one another through a suitable arrangement. Theirposition relative to one another is adjusted while the pulleys arerunning to achieve a variation in the effective diameter of the pulleyassembly and in turn vary the speed of the blower which is driven by thepulley assembly.

Several problems arise when a pulley assembly of this type is used in afield-going corn sheller. The operator of the vehicle which carries thesheller or other harvesting machines must frequently dismount from thedriving position and adjust the pulley while the various driving beltsand movable apparatus is in operation, which is a safety hazard.

Therefore, it is an object of the present invention to provide avariable pulley assembly which can be accurately and quickly adjustedwhen the pulley assembly is in a static state.

The above ends are achieved by a variable pulley assembly adapted tohave a belt tightly trained thereover. The assembly comprises first andsecond sheaves mounted on a shaft for rotation'and axially displaceablerelative to one another. The displacement of the first sheave isadjustably positioned away from the second sheave only when the shaft isin a static state. The displacement of the second sheave toward thefirst sheave is limited. The second sheave is yieldably urged toward itsdisplacement limit by a force low enough to yield in response to thedisplacement of the first sheave toward the second sheave when thepulley assembly is in a static state. However, the force is high enoughto move the second pulley against the displacement unit in opposition tothe frictional forces of the belt during rotation of the pulleyassembly.

The above and other related objects and features of the presentinvention will be apparent from a reading of the description of thedisclosure found in the accompanying drawing and the novelty thereofpointed out in the appended claims.

In the drawing:

FIG. 1 is a longitudinal view of a variable pulley assembly embodyingthe present invention, shown in a position where it has a maximumeffective diameter;

HO. 2 is a longitudinal sectional view of the pulley assembly shown inFIG. 1 showing the manner in which the pulley assembly is adjustedduring a static state.

Referring now to FIG. 1, there is shown a variable pulley assemblyadapted to have a belt 12 tightly trained over first and second sheaves14, 16. The sheaves 14, 16 have central openings 25, 27 in hubs 29, 31,respectively. The sheaves l4, 16 are nonrotatably telescoped over adrive shaft 18 by means of keys 20 and 22, respectively. The keys 20, 22are positioned in appropriate slots in the shaft 18 and are received inaxially extending slots 24, 26 provided in bores 25, 27 of hubs 29 and31.

The shaft 18 is journaled in a bearing assembly 28 suitably secured onthe shaft by a locking collar 30. The bearing assembly 28 is mounted toa wall member 32 on a vehicle in suitable fashion. The belt 12 extendsto another pulley assembly having a fixed or variable diameter. Therelative variation in the effective diameters between this pulleyassembly and pulley assembly 10 produces a variation in speed. It shouldbe apparent that speed variations can be accomplished irrespective ofwhether shaft 18 is the driving or driven shaft.

The sheaves 14, 16 are axially displaceable relative to one another. Thedisplacement of the first sheave 14 away from the second sheave 16 isadjustably limited by a collar 34 which abuts hub 29 of sheave l4 and anut 38 rotatably positioned on a threaded end portion 40 of shaft 18. Asuitable retaining clip 42 acts as a limit to the maximum possibledisplacement of sheave 14 away from sheave 16. This prevents the belt 12from dropping between the sheaves.

The displacement of sheave 16 towards sheave 14 is limited by aretaining clip 44 suitably secured on shaftl8 between the first andsecond sheaves. The sheave 16 is yieldably urged toward retaining clip44 by a spring 48 which abuts an adjusting washer 50 and a backup washer52. The backup washer 52 abuts the retaining collar 30 of the bearing28. A centrally positioned sleeve 54 is positioned so that the hub 31 ofsheave 16 abuts the collar 54 to limit the maximum displacement of thesheave and prevent dropping of the belt 12 between the sheaves.

The free axial movement of the sheaves on the shaft 18 is assured by alubricating system comprising a lubricant fitting 58 threaded into alongitudinal passage 60 in shaft 18. Radial passages 62, 64 .extend fromthe passage 60 to annular recesses 66, 68 on the interior side ofsheaves l4, 16. To insure that lubricant effectively flows irrespectiveof the positions of the sheaves, axially extending recesses 70, 72extend from annular recesses 66, 68.

Since nut 38 is threadedon shaft 18, it rotates with it and it can beonly adjusted when shaft 18 is in a static, nonrotating state. When thebelt 12 is in an intermediate diameter position and it is desired totighten the belt to the position of FIG. 1, the nut 38 is rotated todisplace collar 34 and sheave 14 toward sheave 16. However, since thepulleys are at rest the frictional forces of the belt 12 and sheaves areso great that the belt cannot slide up to a greater effective diameterbetween the sheaves. As a result, the sheave 16 is displaced away fromretaining clip 44 and against the action of spring 48, as shown in FIG.2. When the pulley assembly is rotated, the frictional forces acting tohold the belt 12in the intermediate position are lowered to the pointwhere spring 48 can displace the sheave 16 against retaining clip 44 andurge the belt to an outermost position as shown in FIG. 1.

The spring constant of spring 48 is selected so that it is sufficientlylow to yield in response to displacement of sheave 14 toward sheave 16during a static condition. However, its constant is high enough todisplace the sheave 16 against clip 44 during rotation. This springconstant may be adjusted within limits by adding more adjustment washers50.

For loosening the belt 12 during a static condition it is simplynecessary to rotate nut 38 to permit displacement of collar 34 andsheave 14 away from sheave 16, thereby permitting the belt 12 to ridedown in the V between the pulleys. It is apparent from this that thepulley assembly described above forces an operator to adjust theeffective diameter of the pulley when the pulley assembly is at rest butpermits it to do so in spite of the significant frictional forces thatmust be overcome.

This pulley assembly may be utilized otherwise than as specificallydisclosed without departing from the spirit and scope of the presentinvention. Therefore, it is intended that this invention be limitedsolely by the appended claims.

Having thus described the invention, what is claimed as novel anddesired to be secured by Letters Patent of the United States is:

1. A variable pulley assembly adapted to have a belt tightly trainedthereover, said assembly comprising:

a rotatable shaft;

first and second sheaves mounted for rotation with said shaft butaxially displaceable relative to one another;

an abutment element positioned on said shaft and adjustably positionableonly when the shaft is in a static state for limiting the displacementof said first sheave away from the second sheave;

means for limiting the displacement of the second sheave toward saidfirst sheave;

means for yieldably urging said second sheave toward its displacementlimiting means, said yieldable urging means being adapted to generate aforce low enough to yield in response to the displacement of said firstsheave toward said second sheave when said pulley assembly is in astatic state and high enough to displace said second pulley against saidlimiting means in opposition to the frictional forces of said beltduring rotation of said pulley assembly.

2. A pulley assembly as in claim 1 wherein said adjustable displacementlimiting means comprises a nut threaded on said shaft and a collarpositioned between said nut and said first sheave, whereby rotation ofsaid nut relative to said shaft in a given direction causes said collarto urge said first sheave toward said second sheave.

3. A pulley assembly as in claim 2 wherein said displacement limitingmeans for said second sheave comprises a retaining clip mounted on saidshaft between said first and second sheaves.

4. A variable pulley assembly as in claim 3 wherein said yieldableurging means comprises a spring acting on said second sheave.

5. A variable pulley assembly as in claim 4 wherein said spring has anadjustable abutment to vary the force with which the spring urges thesecond sheave.

6. A variable pulley assembly as in claim 5 wherein:

said shaft has a longitudinal lubricating fluid passage and a pair ofspaced radially extending passages generally in line with said sheaves;

said sheaves are telescoped over said shaft and have an annular recessfor distributing lubricating fluid around the interior of the telescopedportion of said shaft;

said sheaves have recesses axially extending from said annular recessesand are positioned to communicate with said radial passages irrespectiveof the axial displacement of said sheaves.

1. A variable pulley assembly adapted to have a belt tightly trainedthereover, said assembly comprising: a rotatable shaft; first and secondsheaves mounted for rotation with said shaft but axially displaceablerelative to one another; an abutment element positioned on said shaftand adjustably positionable only when the shaft is in a static state forlimiting the displacement of said first sheave away from the secondsheave; means for limiting the displacement of the second sheave towardsaid first sheave; means for yieldably urging said second sheave towardits displacement limiting means, said yieldable urging means beingadapted to generate a force low enough to yield in response to thedisplacement of said first sheave toward said second sheave when saidpulley assembly is in a static state and high enough to displace saidsecond pulley against said limiting means in opposition to thefrictional forces of said belt during rotation of said pulley assembly.2. A pulley assembly as in claim 1 wherein said adjustable displacementlimiting means comprises a nut threaded on said shaft and a collarpositioned between said nut and said first sheave, whereby rotation ofsaid nut relative to said shaft in a given direction causes said collarto urge said first sheave toward said second sheave.
 3. A pulleyassembly as in claim 2 wherein said displacement limiting means for saidsecond sheave comprises a retaining clip mounted on said shaft betweensaid first and second sheaves.
 4. A variable pulley assembly as in claim3 wherein said yieldable urging means comprises a spring acting on saidsecond sheave.
 5. A variable pulley assembly as in claim 4 wherein saidspring has an adjustable abutment to vary the force with which thespring urges the second sheave.
 6. A variable pulley assembly as inclaim 5 wherein: said shaft has a longitudinal lubricating fluid passageand a pair of spaced radially extending passages generally in line withsaid sheaves; said sheaves are telescoped over said shaft and have anannular recess for distributing lubricating fluid around the interior ofthe telescoped portion of said shaft; said sheaves have recesses axiallyextending from said annular recesses and are positioned to communicatewith said radial passages irrespective of the axial displacement of saidsheaves.